This invention relates to a low capacitance solid electrolyte capacitor, and more particularly to a solid electrolyte capacitor with improved electrical properties and reliability at low capacitance rating through the use of an anode assembly of a stub of solid wire for a body portion and a riser portion of a smaller cross-section wire attached thereto. The capacitor provides a lower capacitance rating than is possible with even small porous pellets which are also much more difficult to handle in any manufacturing scheme because of their small size.
Solid electrolytic capacitors having a sintered porous pellet body are well-known in the prior art, as are those in which powder is adhered to a substrate, which may be a wire, so as to form a pellet. Wet electrolytic capacitors which have wire anodes are well-known also. In some of these prior art devices, wire in the form of a helix or coil has been used. In all events, in a wet electrolytic capacitor, the anode is immersed in a liquid electrolyte; and in a solid electrolyte capacitor, the solid electrolyte is deposited on the anode and adheres to it.
The coil or helical configuration of the prior art is not suitable for the present invention as it provides a higher than desired capacitance and CV product because of its high surface area. A completely straight wire anode is also unsatisfactory, in that solid electrolyte tends to be shed from the sides or else wicks to give a non-uniform electrolyte layer.
Porous pellet solid electrolytic capacitors do not suffer from the above adhesion problems, inasmuch as the electrolyte is held on the many surfaces of the pellet. However, even the smallest handleable porous pellets have a relatively high surface area, and hence provide a relatively high capacitance. There is a need in industry today for a solid electrolyte capacitor with lower capacitance than heretofore available at lower cost than a porous pellet would provide.